Measurement of blood flow in the heart and vessels using the Doppler effect is well known. Whereas the amplitude of the reflected waves is employed to produce grayscale images of the tissues, the frequency shift of the reflected waves may be used to measure the velocity of the reflecting scatterers from tissue or blood. Color flow images are produced by superimposing a color image of the velocity of moving material, such as blood, over the grayscale anatomical image. The measured velocity of flow at each voxel determines its color.
Diagnosing and assessing turbulent blood flow through a vessel can be challenging with current ultrasound systems. Normal blood flow may obscure or otherwise make it difficult to visualize part or all of a turbulent flow jet when displayed on a display or monitor. The blood flow jets that occur within the heart during mitral valve or tricuspid valve regurgitations typically have velocities higher than the Nyquist velocity when using color Doppler. Due to aliasing, high velocity blood flow may be detected and displayed incorrectly as low velocity, and thus is not accurately measured.
Previous approaches to overcoming the above problem include adjusting the transparency of flow voxels based on the velocity and variance (or turbulence) of each voxel. However, even in such approaches, noise or artifacts can still be misidentified as jets while short jet bursts may be overlooked or obscured.